1. Field of the Invention
The present invention generally relates to a system and method for adaptive optimization of a testing procedure for integrated circuits being made with given quality control level(s).
2. Description of the Related Art
As the complexity of the semiconductor devices increases, conventional testing methods of integrated circuit (IC) wafers during production involve comprehensive testing methods that greatly require longer time periods to yield useful updated results for production controls resulting in greater cost per yield. Empirical data consistently shows that a relatively small number of tests typically detect all the failures on any given lot of wafer production, but that these tests are not necessarily consistent from lot to lot, or sometimes even wafer to wafer. Furthermore, current methods include manual pattern ordering that does not provide real-time testing based on a set of comprehensive inputs that include current yield results; historical results (at both circuit and product level); and previous test results (wafer in-line test). Manual pattern ordering can take days to weeks depending on an engineer""s time and the amount of data to be analyzed.
Thus, there is a need for minimizing testing time requirements during product (wafer) fabrication yet maintaining acceptable quality control levels, resulting in lower production cost. Moreover, there is a need for a system that can adaptively modify automated production testing equipment using methods that include determining levels of quality control during processing.
In view of the foregoing and other problems, disadvantages, and drawbacks of prior comprehensive testing methods that do not necessarily optimize test procedures for fabricating a product, the present invention has been devised, and it is an object of the present invention to provide a system and method for adaptive optimization of test procedures for a product, which is particularly applicable to production of integrated circuit wafers, given requisite quality control levels. To attain these objects, there is provided, according to one aspect of the invention, a method that minimizes product (wafer or package level) test time without adversely impacting yields in downstream manufacturing processes or degrading outgoing quality levels. The optimization problem here is provided by determining, a priori, the most effective set of tests for a given product (in particular, lot or wafer). In the case of low yielding products, optimizing the sequence of tests for efficient detection of failures also has significant cost benefit to manufacturing tests. The invention includes use of adaptive control applications (e.g., artificial intelligence or expert systems) in a processor-based system that integrates multiple sources of data that include: historical and realtime data of: product specific and lot specific, from product (wafer) fabrication data (i.e., process measurements, defect inspections, and parametric testing), product qualification test results, physical failure analysis results and manufacturing functional test results. These various forms of data are used to determine the best set of tests to run, and the best sequence in which to run them, on a given product, to optimize test time with minimum risk to yield or outgoing quality.
The advantages of this method over other previously used quality control test methods during product production include: using more comprehensive sets of data as inputs to the decision making process of an adaptive controlled testing program for quality control; using fabrication data and correlations between specific fabrication parameters/measurements and test failures; using historical product data combined with lot specific data. The method of the invention integrates both historical and real time data to optimize product testing xe2x80x9con-the-flyxe2x80x9d for effective production controls; and using specialized adaptive control software, to automate data analysis, decision making and test program generation processes.